Treegrid slow performance on drag and drop

We’re experiencing slow performance and memory issues on drag and drop operations in IE using the DHTMLX v2.1 libs. Our application is based upon two treegrids that the user can manipulate with enableDragAndDrop(true). There is NOT a performance problem with initial loading of the trees. However when the user drags and drops, we are running into memory issues. I’ve implemented both onDrag and onDrop and put alert messages in both. The performance problem occurs after the onDrag and before the onDrop (while the trees are in control). The issue occurs when we drag 2000 or more rows. I’ve tried both enableSmartRendering and enableSmartXMLParsing but there is no improvement.

Our domain does not call for the paging approach. Do you have any other suggestions?

This is expected behaviour. If you drag 2000 rows browser should re-render all of them. Re-rendering of 2000 rows is time-consumimg work.
Also note enableSmartRendering() and enableSmartXMLParsing() methods can increase grid performance only while loading data, not while drag-n-drop.
If requirement to drag-and-drop of 2000 rows is critical in your case you can contact and request for component customization.